Method and means for accelerating the ignition of pulverized fuel



June 13, 195$ G. P. JACKSON 2,511,538

METHOD AND MEANS FOR ACCELERATING THE IGNITION OF PULVERIZED FUEL FiledMay 24, 1946 2 Sheets-Sheet 1 INVENTOR. GEORGE P. J19 CIISON June 13,1950 G. P. JACKSON 2,511,588

METHOD AND MEANS FOR ACCELERATING THE IGNITION 0F PULVERIZED FUEL FiledMay 24, 1946 2 Sheets-Sheet 2 I INVENTOR. GEORGE R Jflc/rso/v PatentedJune 13, 1950 UNI-TED F I'CE 2,511,5ss- I min-H01) manners im THEIGNITION or PUILYEIFIZWlTFUE'L George 1?. Jackson, Flushing; Nult, [by

mesne assignments, to Gombusti'on iEngineering-Superheater, 1110., aeorpomtionnf Delaware Application May fi; 1946, No; 2,136

This invention relates tb thecombustien of fuels and particularlyburning fuels that are dinic'ult to ignite, as low volatile coals:

When burning low volatile fuels carried into a -furnace suspendedrinastream of air-it i'srcus tomary to increase the ratio of fuel to soesto obtain a relatively rich mixture. This has been done because it hasbeen found that the speed of flame propagation: is slower .for lowvolatile for high fvolatilefuels and that a material reduction in theair marrying the 101w volatile fuels speeds the burning rate 'oithe.

fuel. The reduced amount ofearrying air slowswhen burning certain low'volatueanthraeites because the primary air needsto he-"reaueedth anamount whieh ap roaches-hr may ev'en m less than that required icrsatisi-adtery eperation of the mill for grinding the iuei' wi'th 'ithe'result th-at "the air swept through the mill is ii-rsufilcient tosatisfaeterily can? ofithe fuel.

On the other hand the amount of primary alrrequired for directlydelivering low 'volaiti-le' fuels from mills-"may be too much forsatisfactory ignition of the fuel. One "methet'l -i'inlfile'yed whenusing an amount of 'air' above the limits coal mixture, between the milland the learner, into two portions, one portion loihgrelativel? rich in"fuel and. the other relatively peer; Elie rich portion is delivered tothe burner anaihto the furnace and the poor portion to a separate nozzlewhich directs it into the furnace to mix with the rich fuel stream at alocation where the fuel portion has attained satisfactory lgm tic-n. Toaccomplish this separation requires special separating apparatus betweenthe will and burner or separating means within the burner. v

"It is an object of this invention to over 'e the above difficulties byproviding means and a 'novel method for burning low- "infla tile fuels.1

In the drawings:

Figure '1 is a vertical 'cross sebum 3 Glaimsr (Cl. lib--28) gtheifairnacehf a steam generator embodying the invention.

Figure 2 is a fragmentary sectional elevationchr-anremarged-scaleshowing the burners of Fig. land zignition eu' dingauxiliary air nozzles therefomrloeated in a wall z-adjacent to that ofthe n3 is, a diagrammatic View illustrating thel relaticnrzbetween thefuel and auxiliary air streams in FigHr-e a superheater I51:Pnlverized'fuel is delivered to the furnac'e bhrnugh'am offset arch [6by means burners-ill; There are usually a multiplicity burners inahnement. The fuel A flows wl'iilelburning within the furnace ancliastheafuelegasmix'ture approaches the bott'omit make-ant "tinn at bend i8and rises up threughjthe furnace to pass thereafter through thescreenrtubes I9, thesup'erheater'ilfi, convection 'banlcilaranxieconcmizer I4 to olftake -20.

I11 o'riler to induce a crossfiow of hot gases ast the 'iuel stream-siA-Iat their points of enwanee into the rurhaee, auseismade of auxiliarynozzles 2| placed in the front wall-2'5 Just below esshownin Figsrl and2, so-a's to fiiheat :j e'ts o'f :nuidiB at substanti'ally right anglestoth'e fclets'ofifrueliA :from burners lLzand between the burners asiihdieated in Fig. 3. whese 21 preferably project their fluid at ahigher velocity than that of the entering tuelstreams and for thispurpose they may satisfa'o'terily receive air under pressure from anysuitable souhce suchas an air "duct 22 through al mpriate cohneetions(not 'show n) therewith. The hur ners 1 1. mayhave' the usual secondaryair channels 23 (see Fig. 2) surrounding the primary air and-' iuel*nezzles '22 which secondary air enamels may receive "theirair from duct22 threugh a uamper-centreueu connection 25.. In the frbhtwall fi "of'furnac'e I'll there may be auditienm hue-teal (see Fig; 1) for the urose of admitting additional air for combustion as the-fuel streams Apass downwardly past them.

Proieeting through the rear wall 28 of furnace Iiiare nozzles- 29{for-directing further air into the r-urnaee receive their air directfrom dill-5t Y i I 7 i hayeifmindithat by arranging the-air nozzleszil"atisubstantially rightangles to and generally ihwbetween' theburner-"nozzles 24 as represented by Figs. 1-2-3, and. that if the airstreamsB tween the fuel streams A and the front wall 26.

As shown by the arrows in the Figure 1, thisup ward flow C comprisesburningf'fuel' removed, I from the outer layers of the fuel streams Aand may include some of the air issuing fromtheupper air ducts 21adjacent the front wall. Not only a is this burning fuel and gas Ctaken-'fromithefuel tream extremely hot but the air joining it alsobecomes extremely hot f rom, heating in the furnace and by participatingin combustion;

Thus, as the mixture ofthe two passes between 7 the adjacent fuel jets Abelow the arch [6 it adds a substantial "amount of heat to the entering.fuel jets A thereby accelerating the rate of.igni-' tion of 'the' fuel.i

- I have found that in burning low'volatilefuels such as anthracite'coalit is difficult to main-. tain ignition at some'distance from theburner, even with a low quantity of primary air, .without the use of theair through air nozzles 2|. When injecting airthrough'the nozzles 2| ata relatively high velocity and creating. said crosscurrents ofburning-fuel between the jets Aissuing from the 5 fuel burned nozzles24, ignition occurs closely adjacent the fuel nozzles 24 and it isossible to substantially increase the amount of primary 'air." With theuse of. the high; velocity jets B throughair nozzles-2| itis possible toincrease the amount of primary air entering the furnace with the fuel tothe quantitynecessary for successful removal of the pulverized fuel fromthe mill.- In this manner, the fuel may;-

be delivered directly from mill to burner andzit becomes unnecessary toemploy separating means in the 'conduit'betWeen-the mill and the burnersor in the burners in order to reduce the quantity of primaryair toenrich the fuel mixture issuing from theburners and'then injecting theseparated coal air mixture atother points into the furnace.

Obviously the high velocity air jets B may be produced by means ofsteamjets placed within the air nozzles 2|. to give the air the requiredvelocity. Or, steam jets alone, may be used to induce the flow of gasespast the entering jets of fuel. I The nozzles 29 projecting through therear wall 28 of the furnace deliver jets of air at relatively Apreferred form of burner nozzle is one that causes the primary air andfuel stream to issue therefrom with its outer surfaces in a turbulentstate. The advantage of this condition is that the turbulent fuel of theouter surfaces of the fuel stream nearest the front wall 26 of thefurnace will more easily commingle with the air entering from ducts 21through the front wall 3-26 and will more quickly burn to furnish heatfor igniting the incoming fuel as described above.

In the form illustrated this surface turbulence is accomplished byintroducing into the burner 1: nozzle 24-a.restriction 3| (see Fig. 2)forming a .sharp edged orifice 32. Preferably the bottom of the'nozzle24, beyond orifice 32, with respect to the fuel flow will have its sides33 flared as 4 shown.

high velocities which act to cause a turbulence in the rising burningfuel-gas stream and thereby increase the rate at which the remainingfuel particles burn. 1 .5

By means of the high velocity air jets B issuing transversely to thefuel streams A as herein disclosed I am able to induce. hot currents Cof burning fuel and gas to flow past the fuel jets issuing from theburners ,to cause ignition to occur substantially at the burner nozzle,thereby, more effectively utilizingthe entire furnace volume.. By meansof the high velocity air jets D issuing through the rear toward thefront wall, I am able to cause greater turbulence and thereby more rapidcombustion and to control the flow path of the fuel-gas mixture throughthe furnace, both of which actions further aiding in more effectivelyutilizing theentire furnace volume. a j I t- While I have shown anddescribed a preferred embodiment of my invention with a vertical type ofburner, it will be understood that the invention' may be adapted to thehorizontal and other types of burners without-departing from the spirit'andscope of the invention as claimed.

' This application is a continuation-in-part of United Statesapplication Serial No. 624,899, filed October 26, 1945. u

What'I claim is:

1. In a furnace having a row of spaced burners for'projecting streams ofa fuel and air mixture in a" downward direction into the furnace and inspaced relation to a furnace sidewall that runs generally parallel tothe burner row; nozzles located in said side-wall of the furnace andmounted in spacedrelationin the intervals berect heating-to thoseair-fuel streams and thereby duced at a given velocity; burning the fuelso in-i troduced in a flame; delivering into the furnace atone sideofsaid fuel-laden primary air stream a supplemental stream of further airwhich has avelocity substantially higher than the primary streams saidgiven velocity;- and directing said supplemental air stream past; saidone side of the enteringprimary stream adjacent and generallytransversely thereto so as to produce, due to the supplemental streamshigher velocity and the relative direction of the two streams, anentrainingqaction which induces from the surface of a burning portion ofthe primary fuel-air stream a current ofthatstreams burning fuel-airmixtureand which causes said current of the aforesaidhot mixture to flowtransversely past a colder portion of. the-.gincoming primary stream ofair and fuel .adlaent its point of delivery into the furnace, theaforesaid transverse flow of said not ignition of said fuel andaccompanying intensification of said flame. I ,J 3. In a method ofburning fuel in a furnaceand 5 accelerating the ignition of that fuel,the steps which comprise delivering said fuel into the furnace inflotation in a stream of primary air introduced downwardly at a givenvelocity; burning the fuel so introduced in a stream; delivering vasupplemental stream of further air substantially horizontally into thefurnace at one side of said fuel-laden primary air stream and at avelocity substantially higher than the primary streams said givenvelocity; and directing said supplemental stream past said one side ofthe entering primary stream adjacent and generally transversely theretobut in out of contact spacing therefrom so as to produce, due to thesupplemental streams higher velocity and the relative direction of thetwo streams, an entraining ,action which induces from the surface of theburning primary fuel-air stream a current of that streams burningfuel-air mixture and which causes said current of the aforesaid hotmixture to flow transversely past a colder portion of said incomingprimary fuel-air stream with resultant acceleration in the ignition ofsaid fuel and accompanying intensification of said flame.

GEORGE P. JACKSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 111,288 Whelpley et al Jan. 24,1871 812,193 Eldred Feb. 13, 1906 1,149,734 Coutant Aug. 10, 1915 i01,258,654 Gram Mar. 12, 1918 1,441,721 Caracriste Jan. 9, 1923 1,670,276Worthington May 15, 1928 1,738,636 Caracristi Dec. 10, 1929 1,754,277Lundgren Apr. 15, 1930 15 1,866,404 Frisch et'al. July 5, 1932 2,293,736Heller Aug. 25, 1942 2,293,737 Hardgrove Aug. 25, 1942 FOREIGN PATENTSNumber Country Date 331,555 Great Britain July 4, 1930

